[PATCH] selftests: vDSO: Fix header search list for vgetrandom-chacha.S

[Thomas Huth]

On aarch64, vgetrandom-chacha.S includes the assembler file from
arch/arm64/kernel/vdso/vgetrandom-chacha.S, and that includes
<asm/assembler.h> which in turn includes lots of system header files.
For this, we should make sure that the kernel headers of the
*current* kernel are in the search path of the compiler, otherwise
we end up including headers from /usr/include of the current distro
instead, and this is calling for trouble! Thus use $(KHDR_INCLUDES)
here to make sure that we are using the right header files.
(This issue has been found in a patch series that replaces __ASSEMBLY__
with __ASSEMBLER__ in the various kernel headers and finally stops
defining __ASSEMBLY__ in the kernel makefiles - when vgetrandom-chacha.S
now tries to include a header from /usr/include the compilation fails
since those headers still require __ASSEMBLY__ to fence away the C code)

Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx>
---
 See this link for the build failure:
 https://lore.kernel.org/oe-kbuild-all/9e294bfd-4704-42a5-a704-f301f4afe042@xxxxxxxxxxxxxxxx/

 tools/testing/selftests/vDSO/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/vDSO/Makefile b/tools/testing/selftests/vDSO/Makefile
index a61047bdcd576..1af346ac87081 100644
--- a/tools/testing/selftests/vDSO/Makefile
+++ b/tools/testing/selftests/vDSO/Makefile
@@ -37,7 +37,8 @@ $(OUTPUT)/vdso_test_getrandom: CFLAGS += -isystem $(top_srcdir)/tools/include \
                                          -isystem $(top_srcdir)/include/uapi
 
 $(OUTPUT)/vdso_test_chacha: vgetrandom-chacha.S
-$(OUTPUT)/vdso_test_chacha: CFLAGS += -idirafter $(top_srcdir)/tools/include \
+$(OUTPUT)/vdso_test_chacha: CFLAGS += $(KHDR_INCLUDES) \
+                                      -idirafter $(top_srcdir)/tools/include \
                                       -idirafter $(top_srcdir)/tools/include/generated \
                                       -idirafter $(top_srcdir)/arch/$(SRCARCH)/include \
                                       -idirafter $(top_srcdir)/include \
-- 
2.56.0